JP2010156791A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which can prevent the position of a tandem type photosensitive drum unit with respect to an apparatus body from deviating when a developing roller is separated from a photosensitive drum. <P>SOLUTION: An oscillation member 280 is supported so as to be oscillated by a first supporting shaft 239 provided so as to protrude from the drum unit 204. A translation cam 302 is provided in a body casing 202 so as to be movable linearly in a front-rear direction. The translation cam 302 abuts on the abutting portion 284 of the oscillation member 280 during linear movement. The pressing portion 286 of the oscillation member 280 presses a developing pressing boss 260 in a direction in which the developing roller 207 is separated from the photosensitive drum 205 with the linear movement after the translation cam 302 abuts on the abutting part 284. The oscillation member 280 includes a spring portion 287. The spring portion 287 has biasing force in a direction in which the pressing portion 286 is moved to be separated from the developing pressing boss 260. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a color laser printer.

As an electrophotographic color printer, a so-called tandem type printer is known in which photosensitive drums corresponding to yellow, magenta, cyan, and black are arranged in parallel.
A tandem type color printer is provided with a developing unit that holds a developing roller facing each photosensitive drum. An electrostatic latent image is formed on the surface of the photosensitive drum. When the electrostatic latent image faces the developing roller with the rotation of the photosensitive drum, toner is supplied from the developing roller to the electrostatic latent image. As a result, a toner image is formed on the surface of the photosensitive drum. A toner image of a corresponding color is formed on each photosensitive drum, and the toner image of each color is transferred onto the paper conveyed by the belt, thereby forming a color image on the paper. In addition, a black toner image is formed only on the black photosensitive drum, and the black toner image is transferred onto the paper, thereby forming a monochrome image on the paper.

When a monochrome image is formed, a toner image is not formed on yellow, magenta, and cyan photosensitive drums other than black. Therefore, it is desirable to separate the developing roller from these photosensitive drums to prevent the developing roller from being consumed.
Accordingly, as a tandem type image forming apparatus, a linear motion cam member that is linearly movable in the arrangement direction of the photosensitive drums and a linear movement of the linear motion cam member are displaced, and the developing device is pressed upward to develop the photosensitive drum. The thing of the structure provided with the intermediate member for separating from a roller is proposed (for example, refer patent document 1). Due to the linear movement of the linear cam member, the development roller is separated from all the photosensitive drums, and the development roller contacts the black photosensitive drum, and the development rollers are separated from the yellow, magenta, and cyan photosensitive drums. The state is switched between a black contact state and an all-color contact state in which the developing roller contacts all the photosensitive drums.

Further, in the image forming apparatus according to this proposal, the photosensitive drums of four colors are integrally held by the drum unit, and the drum unit can be attached to and detached from the apparatus main body. Each color developer is detachably attached to the drum unit.
JP 2007-178654 A

However, in the configuration according to the conventional proposal, when the developing device is pressed upward by the intermediate member, the position of the drum unit with respect to the apparatus main body may be shifted due to the force applied from the intermediate member to the developing device. When the position of the drum unit is shifted, the position of the image formed on the sheet is shifted with the shift.
SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of preventing the position of a tandem type photoreceptor unit relative to the apparatus main body from being shifted when a developing roller is separated from a photosensitive drum.

  In order to achieve the above object, according to a first aspect of the present invention, in the image forming apparatus, the apparatus main body and the plurality of photosensitive drums are integrally held in a state of being arranged in parallel, and A tandem type photosensitive unit that is mounted so as to be movable along the direction in which the photosensitive drums are arranged; and a developing roller that is provided corresponding to each of the photosensitive drums and supplies developer to the corresponding photosensitive drum. A developing cartridge that is held and detachably attached to the tandem photoconductor unit, a linear motion member that is linearly movable in the arrangement direction in the apparatus main body, and each of the developing cartridges. A first support shaft provided on the tandem photoconductor unit, and a swing member supported swingably on the first support shaft. The swing member is disposed on the first support shaft. Against A contact portion provided on one side, on which the linearly moving member contacts during linear movement, and provided on the other side of the first support shaft, facing a predetermined portion of the developing cartridge, and Along with the linear movement after contact with the contact portion, a pressing portion that presses the predetermined portion in a direction in which the developing roller separates from the photosensitive drum, and a movement in the direction in which the pressing portion moves away from the predetermined portion. And a spring portion having an urging force in the direction to be moved.

According to a second aspect of the present invention, in the first aspect of the present invention, the spring portion is elastically deformed in contact with the tandem type photoreceptor unit.
According to a third aspect of the present invention, in the first or second aspect of the present invention, the swinging member is configured so that the inner side in the axial direction is lower than the outer side in the axial direction of the photosensitive drum. It is characterized by having a guide part which inclines with respect to.

  According to a fourth aspect of the invention, in the invention according to any one of the first to third aspects, the apparatus main body has a main body reference axis extending in an axial direction of the photosensitive drum, and the tandem type photoconductor. When the unit is mounted in the apparatus main body, the unit abuts against the main body reference axis, and the direction in which the tandem photosensitive unit abuts against the main body reference axis, The direction of the pressing force applied to the abutting portion of the swing member is substantially the same.

According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the linear motion member is provided corresponding to each of the swing members, and the contact of the swing member is A cam portion for contacting the contact portion and pressing the contact portion is provided.
According to a sixth aspect of the present invention, in the fifth aspect of the present invention, all the cam portions abut on the abutting portion of the swinging member due to the linear movement of the linear motion member. A first state; a second state in which at least one of the cam portions abuts against the contact portion of the swing member; and a third state in which all the cam portions are separated from the contact portion of the swing member. It is arranged so that it can be taken.

  According to a seventh aspect of the invention, in the sixth aspect of the invention, the developing cartridge is provided corresponding to each color of black, yellow, magenta, and cyan, and the second state is yellow, magenta And the cam portion is in contact with the contact portion of each swing member corresponding to cyan, and the cam portion is separated from the contact portion of the swing member corresponding to black. Yes.

According to an eighth aspect of the present invention, in the invention according to any one of the fifth to seventh aspects, an abutting surface of the cam portion with the abutting portion of the swinging member is the surface of the photosensitive drum. It is characterized by being formed on an inclined surface inclined with respect to the axial direction.
The invention according to claim 9 is the invention according to any one of claims 1 to 8, and is provided corresponding to each of the developing cartridges, and each of the developing cartridges is attached to the tandem type photoreceptor unit. And a pressing mechanism for pressing each of the developing cartridges in a direction in which the developing roller and the photosensitive drum face each other.

  According to a tenth aspect of the present invention, in the ninth aspect of the invention, the second support shaft provided in the tandem type photoreceptor unit is provided, and the pressing mechanism is swingable with respect to the second support shaft. A pressing member that is supported and abuts against the predetermined part of the developing cartridge and a spring that elastically presses the pressing member against the predetermined part are provided.

  According to the first aspect of the present invention, the plurality of photosensitive drums are held in parallel in the tandem type photoreceptor unit. In addition, a developing cartridge that holds the developing roller is detachably attached to the tandem type photoreceptor unit. The tandem type photoreceptor unit is provided with a swing member corresponding to each developing cartridge. Each oscillating member is slidably supported by a first support shaft protruding from the tandem photoconductor unit. The tandem photoconductor unit is mounted in the apparatus main body so as to be movable along the alignment direction of the photosensitive drums (hereinafter, simply referred to as “alignment direction” in this section). A linear motion member is provided in the apparatus main body so as to be linearly movable in the arrangement direction. A contact portion is provided on one side of the swing member with respect to the first support shaft. The linear movement member contacts the contact portion during linear movement. A pressing portion is provided on the other side of the swing member with respect to the first support shaft. The pressing portion faces a predetermined portion of the developing cartridge, and presses the predetermined portion in a direction in which the developing roller separates from the photosensitive drum in accordance with the linear movement after the linear movement member contacts the contact portion. Further, the swing member has a spring portion. The spring part has a biasing force in a direction to move the pressing part in a direction away from the predetermined part.

  In a state where each developing cartridge is mounted on the tandem type photoconductor unit, the pressing portion of the swinging member faces a predetermined portion of each developing cartridge. Due to the linear movement of the linear motion member, the contact portion of the swinging member is pressed against the linear motion member, and the pressing portion of the swinging member presses a predetermined portion of the developing cartridge in a direction in which the developing roller is separated from the photosensitive drum. Thereby, the developing roller can be separated from the photosensitive drum. Further, when the linear motion member is linearly moved from that state, the pressing of the contact portion of the swinging member by the linear motion member is released, and the pressing of the predetermined portion of the developing cartridge by the pressing portion of the swinging member is released. The

  As described above, the swinging member is supported on the first support shaft provided in the tandem type photoreceptor unit, and the swinging member swings about the first support shaft, so that the developing roller is moved with respect to the photosensitive drum. Connect and separate. Therefore, even if a pressing force is applied from the linear motion member to the swinging member, the pressing force does not directly act on the tandem type photoreceptor unit. As a result, when the developing roller is separated from the photosensitive drum, it is possible to prevent the position of the tandem type photosensitive unit relative to the apparatus main body from shifting.

Further, when the pressing of the predetermined portion of the developing cartridge by the pressing portion of the swing member is released, the pressing portion moves in a direction away from the predetermined portion by the biasing force of the spring portion. As a result, the posture of the swing member can be stably maintained at a position where the pressing portion of the swing member does not press the predetermined portion of the developing cartridge.
According to the second aspect of the present invention, the spring portion abuts on the tandem photoconductor unit and elastically deforms. Thereby, the biasing force of the spring portion can be effectively applied to the swing member.

  According to the invention described in claim 3, the swing member includes the guide portion. The guide portion is inclined with respect to the axial direction so that the inner side in the axial direction is lower than the outer side in the axial direction of the photosensitive drum. Thus, when the developing cartridge is mounted on the tandem photosensitive unit, the developing cartridge is guided inward in the axial direction of the photosensitive drum by moving a predetermined portion of the developing cartridge along the guide portion. The As a result, the developing cartridge can be easily aligned in the axial direction.

  According to the fourth aspect of the present invention, the apparatus main body has the main body reference axis extending in the axial direction of the photosensitive drum. The tandem photoconductor unit is in contact with the main body reference axis in a state of being mounted in the apparatus main body. By this contact, the tandem type photoreceptor unit is positioned with respect to the apparatus main body. The direction of the pressing force applied from the linear motion member to the abutting portion of each swinging member is substantially the same as the direction in which the tandem photosensitive unit abuts against the main body reference axis. Therefore, even if a force acts on the tandem photoconductor unit through the swinging member from the linear motion member, the force is substantially in the same direction as the direction in which the tandem photoconductor unit abuts against the main body reference axis. It is power. Therefore, when the developing roller is separated from the photosensitive drum, it is possible to prevent the position of the tandem photosensitive unit relative to the apparatus main body from shifting.

  According to the fifth aspect of the present invention, the linear motion member is provided with the cam portion for pressing the contact portion of the swing member corresponding to the swing member. When the cam portion comes into contact with the contact portion of the swing member, the contact portion of the swing member is pressed by the cam portion. On the other hand, when the cam portion is separated from the contact portion of the swing member, the pressing of the contact portion of the swing member by the cam portion is released. Therefore, the rocking member can be swung by a simple configuration in which the cam portion is provided on the linear motion member, and the developing roller can be separated from the photosensitive drum.

According to the sixth aspect of the present invention, the first state in which all the cam portions abut on the abutting portion of the oscillating member by the linear movement of the linear motion member, and at least one cam portion abuts the oscillating member. It is possible to switch between a second state in which the other cam portions are in contact with the contact portion and separated from the contact portion of the swing member, and a third state in which all the cam portions are separated from the contact portion of the swing member. .
According to the seventh aspect of the present invention, the developing cartridge is provided corresponding to each color of black, yellow, magenta and cyan. In the first state, the cam portions come into contact with the contact portions of the swing members for all colors, so that the development rollers for all colors are separated from the photosensitive drums. In the second state, the cam portions come into contact with the contact portions of the swinging members corresponding to yellow, magenta, and cyan, so that the yellow, magenta, and cyan developing rollers are separated from the photosensitive drum, and the black developing roller is Touch the photosensitive drum. In the third state, the developing roller for all colors comes into contact with the photosensitive drum by separating the cam portion from the contact portion of the swinging member for all colors. Therefore, by setting the second state when forming a monochrome image, it is possible to prevent the yellow, magenta, and cyan developing rollers from being consumed.

  According to the eighth aspect of the present invention, the contact surface of the cam portion with the contact portion of the swing member is formed as an inclined surface that is inclined with respect to the axial direction of the photosensitive drum. Therefore, the pressing force applied from the cam portion to the abutting portion of the swing member includes a force component in the axial direction of the photosensitive drum. As a result, since the axial force of the photosensitive drum acts on the tandem photosensitive unit, the tandem photosensitive unit can be positioned in the axial direction.

According to the ninth aspect of the present invention, a pressing mechanism for pressing the developing cartridge in the opposing direction of the developing roller and the photosensitive drum is provided corresponding to each developing cartridge. With this pressing mechanism, the developing roller can be pressed against the photosensitive drum. As a result, the developer can be satisfactorily supplied from the developing roller to the photosensitive drum.
According to the tenth aspect of the present invention, the tandem photoconductor unit is provided with the second support shaft. A pressing member is supported on the second support shaft in a swingable manner, and the pressing member is elastically pressed against a predetermined portion of the developing cartridge by a spring. By this pressing, the developing roller can be pressed against the photosensitive drum.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
1. Printer FIG. 1 is a side sectional view showing an embodiment of a printer as an example of an image forming apparatus of the present invention. In addition, when referring to a direction, the illustrated direction arrow is referred to (the same applies to other drawings). Here, the horizontal direction and the width direction are the same, and the vertical direction and the vertical direction are the same. The horizontal direction includes the width direction and the front-rear direction.

The printer 201 is a tandem color laser printer. The printer 201 includes a main body casing 202 as an example of an apparatus main body. A front cover 203 is provided on one side of the main casing 202 so as to be openable and closable.
A drum unit 204 as an example of a tandem type photoreceptor unit is provided in the main body casing 202. The drum unit 204 can be attached to and detached from the main body casing 202 through an attachment / detachment opening formed on the front surface of the main body casing 202 with the front cover 203 opened.

  In the drum unit 204, four photosensitive drums 205 are arranged in parallel along the front-rear direction in a rotatable state. On each photosensitive drum 205, a scorotron charger 206 and a developing roller 207 are arranged to face each other. Each photosensitive drum 205 is adjacent to a developing cartridge 208 that holds a developing roller 207 and contains toner (developer). The developing cartridge 208 is configured to be detachable from the drum unit 204. The toner of the developing cartridge 208 is carried on the surface of the developing roller 207.

  The surface of each photosensitive drum 205 is uniformly charged by the charger 206 and then exposed by a laser beam (see the broken arrow in the drawing) emitted from the scanner unit 209 provided on the upper portion of the main body casing 202. Thereby, an electrostatic latent image based on the image data is formed on the surface of each photosensitive drum 205. The electrostatic latent image on each photosensitive drum 205 is visualized by toner carried on the surface of the developing roller 207 corresponding to each photosensitive drum 205, and a toner image is formed on the surface of each photosensitive drum 205. The Here, since the color of the toner accommodated in each developing cartridge 208 differs depending on each developing cartridge 208, the color of the toner image on each photosensitive drum 205 differs depending on each photosensitive drum 205.

  At the bottom of the main casing 202, a paper feed cassette 210 that stores the paper S is disposed. The paper S accommodated in the paper feed cassette 210 is transported onto the transport belt 211 by various rollers. The conveyor belt 211 is disposed to face the four photosensitive drums 205 from below. A transfer roller 212 is disposed at each position facing the photosensitive drum 205 across the upper portion of the conveyance belt 211. The sheet S transported on the transport belt 211 sequentially passes between the transport belt 211 and each photosensitive drum 205 as the transport belt 211 travels. The toner image on the surface of the photosensitive drum 205 is transferred to the sheet S by the transfer bias applied to the transfer roller 212 when facing the sheet S.

A fixing device 213 is provided on the downstream side in the conveyance direction of the sheet S with respect to the conveyance belt 211. The sheet S on which the toner image is transferred is conveyed to the fixing device 213. In the fixing device 213, the toner image is fixed on the paper S by heating and pressing. The sheet S on which the toner image is fixed is discharged to a discharge tray 214 on the upper surface of the main body casing 202 by various rollers.
2. Drum Unit FIG. 2 is a perspective view of the drum unit as viewed from the upper left front side, showing a state in which one developing cartridge is attached and the other developing cartridges are detached. FIG. 3 is a perspective view of the drum unit as viewed from the upper left front side, showing a state where one developing cartridge is being attached and detached and the other developing cartridges are detached. FIG. 4 is a front view of the drum unit.

As shown in FIG. 2, the drum unit 204 includes four photosensitive drums 205, four developing cartridges 208, four drum subunits 220, a front beam 221, a rear beam 222, a pair of first side plates 223, and a pair of second plates. The side plate 224 is integrally attached to and detached from the main body casing 202 (see FIG. 1).
(1) Drum subunits The four drum subunits 220 are arranged between the pair of first side plates 223 with a space in the front-rear direction. Each drum subunit 220 is made of resin, and is formed in a substantially triangular prism shape that is elongated in the width direction and opened to the lower front side. Each drum subunit 220 holds a charger 206 shown in FIG. 1 and a cleaning member (not shown) for cleaning the surface of the photosensitive drum 205.
(2) Front beam The front beam 221 is made of resin. The front beam 221 is installed between the front end portions of the pair of first side plates 223.

The front beam 221 holds a support shaft 225. The support shaft 225 is disposed so as to penetrate the front beam 221 along the width direction, protrudes outward in the width direction from the front beam 221, and further penetrates the first side plate 223 and the second side plate 224 to outward in the width direction. Protruding.
A front grip 226 is rotatably supported on the support shaft 225. The near side grip 226 is disposed at the center in the width direction of the front beam 221. The front side gripping part 226 is substantially U-shaped, and each free end is rotatably supported by the support shaft 225. The storage position where the front side gripping part 226 stands along the front beam 221 and the front side of the front beam 221 are provided. It is provided so as to be swingable at an operation position that tilts toward the center.
(3) Rear beam The rear beam 222 is made of resin. The rear beam 222 is installed between the rear end portions of the pair of first side plates 223.

A back side grip 227 is integrally formed at the center in the width direction on the upper surface of the rear beam 222. The rear gripping part 227 is substantially U-shaped when viewed from the back, and each free end thereof is connected to the rear beam 222, is inclined from the lower rear side to the front upper side, and protrudes obliquely upward from the rear beam 222. It has been.
(4) 1st side board FIG. 5: is the left view which cut | disconnected a drum unit partially.

The left and right first side plates 223 are produced by pressing a metal plate using the same press mold and have the same shape.
As shown in FIG. 5, the first side plate 223 is formed in a substantially elongated rectangular plate shape extending in the front-rear direction. The front end portion and the rear end portion of the first side plate 223 are opposed to the front beam 221 and the rear beam 222 shown in FIGS. 2 and 3, respectively, in the left-right direction.

The front end portion of the first side plate 223 extends toward the front upper side. A support shaft insertion hole 230 is formed through the front end portion of the first side plate 223. A support shaft 225 is inserted through the support shaft insertion hole 230.
The rear end portion of the first side plate 223 is formed in a substantially L shape in a side view. More specifically, the rear end portion of the first side plate 223 is formed in a shape that inclines toward the rear upper side and extends further upward.

In addition, a notch portion 231 having a shape that is notched in a substantially V shape from the rear end edge is formed at the rear end portion of the first side plate 223. Specifically, the notch 231 includes an upper end edge extending in the front-rear direction in a side view, a lower end edge inclined at a constant gradient upward in the front side, and a front end edge connecting the front end of the upper end edge and the front end of the lower end edge. It is formed in the shape to have.
Four circular drum support holes 232 are formed in the first side plate 223. The drum support holes 232 are formed between the front end portion and the rear end portion of the first side plate 223 at a predetermined interval in the front-rear direction. The end in the width direction of the photosensitive drum 205 is inserted into each drum support hole 232. As a result, each photosensitive drum 205 is held between the pair of first side plates 223.
(5) Second Side Plate FIG. 6 is a left side view of the right second side plate.

  The second side plate 224 is made of, for example, fiber reinforced resin. As shown in FIG. 5, the second side plate 224 is formed in a substantially elongated rectangular plate shape in side view having a width that is wider in the vertical direction and substantially the same length in the front-rear direction as compared with the first side plate 223. The front end portion and the rear end portion of the second side plate 224 are opposed to the front beam 221 and the rear beam 222 shown in FIGS. 2 and 3, respectively, in the left-right direction.

The front end portion of the second side plate 224 is formed to be narrower in the vertical direction than the middle portion of the second side plate 224, and the lower end edges thereof are inclined upward in the front side. Further, the rear end portion of the second side plate 224 is formed to be narrower in the vertical direction than the middle portion of the second side plate 224, and the lower end edge thereof is inclined upward toward the rear side.
As shown in FIGS. 2 and 3, a flange 233 extending outward in the width direction over the front-rear direction is formed at the upper end of each second side plate 224. An inclined surface 234 is formed at the front end portion of the flange portion 233 so as to incline from the lower surface toward the front upper side.

  As shown in FIG. 5, the front end portion of the second side plate 224 is formed narrower in the vertical direction than the middle portion of the second side plate 224, and the lower end edge thereof is inclined toward the front upper side. As shown in FIG. 6, a support shaft insertion hole 235 is formed at the front end of the second side plate 224. The support shaft insertion hole 235 is formed at a position facing the support shaft insertion hole 230 (see FIG. 5) of the first side plate 223 in the width direction.

  As shown in FIG. 5, the rear end portion of the second side plate 224 is formed to be narrower in the vertical direction than the middle portion of the second side plate 224, and the lower end edge thereof is inclined toward the rear upper side. Yes. As shown in FIG. 6, a notch 236 is formed at the rear end of the second side plate 224. The notch 236 is formed in substantially the same shape as the notch 231 at a position facing the notch 231 (see FIG. 5) of the first side plate 223 in the width direction.

  On the inner side in the width direction of the second side plate 224 (the right side surface of the left second side plate 224 and the left side surface of the right second side plate 224), the developing cartridge 208 between the left and right second side plates 224 (FIG. 2 and FIG. 2). 4), four cartridge guide portions 237 for guiding attachment / detachment are formed at regular intervals in the front-rear direction. The cartridge guide portion 237 is formed of two protrusions that protrude inward in the width direction from the inner side surface of the second side plate 224 and are spaced from each other. The cartridge guide part 237 is inclined at a constant gradient from the upper end part of the second side plate 224 toward the lower rear side, and is connected to the cartridge holding part 238. The cartridge holding part 238 is formed in parallel to a line connecting the center of the photosensitive drum 205 and the center of the developing roller 207 shown in FIG. 1, and its lower end is opened toward the photosensitive drum 205.

In addition, four first support shafts 239 project from the upper end portion of the inner side surface of the second side plate 224 at a predetermined interval in the front-rear direction. In addition, four second support shafts 240 project from the upper end portion of the inner side surface of the second side plate 224 at a predetermined interval in the front-rear direction. Each of the second support shafts 240 is disposed at a position spaced in front of each of the first support shafts 239.
A swing member 280 is swingably supported on each first support shaft 239. Further, a pressing cam 271 as an example of a pressing member is supported on each second support shaft 240 in a swingable manner. Specific configurations of the swing member 280 and the pressing cam 271 will be described in detail later.
(5-1) Left Second Side Plate As shown in FIGS. 2 and 3, the left second side plate 224 is formed with a drum coupling insertion hole 242 that exposes the left end in the axial direction of each photosensitive drum 205. ing.

  Four drum coupling insertion holes 242 are formed at the lower end portion of the second side plate 224 at intervals from each other along the front-rear direction. The drum coupling insertion hole 242 penetrates the second side plate 224 in the thickness direction at a position facing the left end in the axial direction of each photosensitive drum 205 and the drum support hole 232 provided in the first side plate 223 in the width direction. It is formed as a round hole.

The second side plate 224 on the left is provided with a development coupling insertion hole 243 at a position above the front side with respect to each drum coupling insertion hole 242. Although not shown in FIGS. 2 and 3, the developing coupling insertion hole 243 is disposed between the two protrusions of each cartridge guide portion 237 formed on the inner surface of the left second side plate 224. And penetrates the second side plate 224 in the thickness direction. As shown in FIG. 2, the developing couplings 261 provided on the left side surface of the developing cartridge 208 are inserted into the developing coupling insertion holes 243 with the developing cartridges 208 mounted between the left and right second side plates 224. Opposite.
(6) Pressing Mechanism As shown in FIG. 5, the drum unit 4 includes four pressing mechanisms 270.

Each pressing mechanism 270 includes a pressing cam 271 as an example of a pressing member, and a pressing spring 272 as an example of a spring that elastically presses the pressing cam 271 downward in the rear side.
The pressing cam 271 is formed in a substantially triangular plate shape when viewed from the side. The second support shaft 240 of the second side plate 224 is inserted through one corner of the pressing cam 271. Accordingly, the pressing cam 271 is supported so as to be swingable with respect to the second side plate 224. The pressing cam 271 is provided in a posture extending obliquely upward on the rear side from a corner portion supported by the support shaft 39.

As shown by a broken line in FIG. 5, the pressing spring 272 is wound around the second support shaft 240, one end of which is locked to the second side plate 224, and the other end is locked to the pressing cam 271. Has been.
(7) Oscillating Member As shown in FIG. 5, the drum unit 4 includes four oscillating members 280.

FIG. 7A is a side view of the swing member, and shows a part of the second side plate. FIG. 7B is a perspective view seen from the upper left rear side of the swing member. FIG. 7C is a perspective view of the swing member as viewed from the upper right rear side.
The swing member 280 is made of a resin material, and has a body portion 281 that is substantially triangular plate-shaped in a side view as shown in FIG. 7A. Specifically, the upper end edge of the main body 281 extends in the front-rear direction. The front end edge of the main body 281 extends downward from the front end portion of the upper end edge, and extends obliquely rearward and downward from the middle portion thereof. The rear end edge of the main body 281 is inclined from the front lower side toward the rear upper side so as to connect the lower end portion of the front end edge and the rear end portion of the upper end edge.

A shaft hole 282 is formed as a round hole penetrating the main body 281 in the left-right direction in the middle of the rear end edge of the main body 281. As shown in FIG. 5, the first support shaft 239 provided on the second side plate 224 is inserted into the shaft hole 282. Thus, the swing member 280 is supported so as to be swingable with respect to the second side plate 224.
As shown in FIG. 7B, two guide portions 283 are formed on the left side surface of the main body portion 281. Each guide part 283 extends along the front-rear direction and is inclined from the upper right side to the lower left side.

7B and 7C, the swinging member 280 includes a contact portion 284 that protrudes rightward from the rear end portion of the upper end edge of the main body portion 281. The contact portion 284 is formed in a substantially trapezoidal shape when viewed from the side, and has a front end surface that forms an inclined surface 285 that is inclined from the upper rear side toward the lower front side.
The swing member 280 includes a pressing portion 286 that protrudes leftward from the lower end portion of the rear end edge of the main body portion 281. The pressing portion 286 is formed in a substantially rectangular shape when viewed from the side, extends in a direction along the radial direction of the shaft hole 282, and in the state shown in FIG. 7A, the upper end is located above the rear side and the lower end is located below the front side. It is arranged in a tilted position.

  Further, as shown in FIG. 7A, the swing member 280 includes a spring portion 287. The spring portion 287 is formed integrally with the main body portion 280 and has an elongated thin plate shape extending vertically downward from a middle portion of the front end edge of the main body portion 281. Thereby, the spring part 287 has the spring property which can be elastically deformed. A projection 288 protruding forward is provided at the lower end of the spring portion 287.

On the other hand, the second side plate 224 is provided with an abutting wall 289 against which the protrusion 288 of the spring portion 287 abuts. The contact wall 289 extends inward in the width direction from the inner side surface of the second side plate 224, and is formed in a substantially inverted L shape in side view.
(7-1) Elastic Deformation of Spring Part FIG. 8 is a side view of the oscillating member, showing a state in which the oscillating member is oscillated in a direction for moving the developing cartridge from the first position to the second position. .

As shown in FIG. 8, the swing member 280 moves the developing cartridge 208 (see FIGS. 2 and 3) from the first position to the second position, that is, the swing member 280 is inserted through the shaft hole 282. When the first support shaft 239 (see FIG. 5) is pivoted in the counterclockwise direction in FIG. 8, the protrusion 288 of the spring portion 287 moves upward on the rear side surface of the contact wall 289. . At this time, the middle portion of the spring portion is elastically deformed so as to bulge outward in the radial direction of the shaft hole 282 as the projection 288 moves. In this state, the spring portion 287 has a biasing force in a direction that causes the swing member 280 to swing in the clockwise direction in FIG.
(8) Photosensitive drum As shown in FIGS. 2 and 3, the photosensitive drum 205 includes a cylindrical drum main body 245 and two flange members 246 that are fitted to both ends of the drum main body 245 so as not to rotate relative to each other. It has.

The outermost layer of the drum body 245 is formed of a positively chargeable photosensitive layer.
The flange member 246 is made of a resin material, and part of the flange member 246 is inserted into both ends of the drum body 245. A coupling groove 247 is formed on the left end surface of the left flange member 246. A drive transmission unit (not shown) provided in the main body casing 202 is coupled to the coupling groove 247. As a result, as shown in FIG. 1, with the drum unit 204 mounted in the main body casing 202, the driving force from the drive transmission unit is transmitted to the photosensitive drum 205, and the photosensitive drum 205 can be rotated.

The left and right flange members 246 are rotatably supported with respect to the drum support holes 232 (see FIG. 5) of the first side plate 223 by bearing members (not shown).
3. Developer Cartridge As shown in FIG. 1, the developer cartridge 208 includes a box-shaped developer frame 251 that is open at the lower rear side. In the developing frame 251, a developing roller 207, a supply roller 252, an agitator 253, and a layer thickness regulating blade 254 are provided.

A part of the circumferential surface of the developing roller 207 is exposed from the developing frame 251 downward to the front side. With the developing cartridge 208 mounted on the drum unit 204, the developing roller 207 has a front upper side with respect to the circumferential surface of the photosensitive drum 205. Abut.
The supply roller 252 is disposed at a position above the front side of the developing roller 207, and its peripheral surface is in pressure contact with the peripheral surface of the developing roller 207.

The agitator 253 is provided at an upper position in the developing frame 251 so as to be rotatable about an axis extending in the width direction.
The layer thickness regulating blade 254 has one end fixed to the developing frame 251 and the other end elastically in contact with the peripheral surface of the developing roller 207.
The developing frame 251 contains toner corresponding to each color.

A part of the toner in the developing frame 251 is supplied to the supply roller 252 while being stirred in the developing frame 251 by the rotation of the agitator 253. The toner supplied to the supply roller 252 is supplied to the developing roller 207 by the contact between the supply roller 252 and the developing roller 207. The toner supplied to the developing roller 207 is regulated in thickness by the layer thickness regulating blade 254 as the developing roller 207 rotates, and is carried on the peripheral surface of the developing roller 207 as a thin layer having a constant thickness. Thus, when the electrostatic latent image formed on the circumferential surface of the photosensitive drum 205 faces the developing roller 207, toner is supplied from the developing roller 207 to the electrostatic latent image, and the electrostatic latent image is developed.
(1) Development Frame As shown in FIG. 3, the development frame 251 has a pair of left and right side walls 255 and a front wall 256, a rear wall 257, and an upper wall 258 that connect the pair of side walls 255. In the side view, it is formed in a substantially triangular shape.

Both end portions in the axial direction of the roller shaft 259 of the developing roller 207 (see FIG. 1) penetrate the lower end portion of the side wall 255 and protrude outward in the width direction.
Further, a development pressing boss 260 as an example of a pressed portion projects from the side wall 255 outward in the width direction at a position above the front side of each side wall 255.
Further, a developing coupling 261 is disposed on the left side wall 255 at a position above the front side with respect to the roller shaft 259. The development coupling 261 is connected to a plurality of gears (not shown) for transmitting a rotational driving force to the development roller 207 and the supply roller 252 (see FIG. 1).

As shown in FIG. 2, each developing coupling 261 faces each developing coupling insertion hole 243 in a state where each developing cartridge 208 is mounted on the drum unit 204. A drive transmission unit (not shown) for transmitting a driving force from a motor (not shown) provided in the main body casing 202 (see FIG. 1) to each developing coupling insertion hole 243. It is inserted. Each drive transmission unit is coupled to each development coupling 261, so that a rotational driving force can be transmitted to the development roller 207 and the supply roller (see FIG. 1) via each drive transmission unit and the development coupling 261. it can.
(2) Mounting of Developing Cartridge to Drum Unit As shown in FIG. 3, the developing cartridge 208 for each color is mounted between the left and right second side plates 224 from above. At this time, both end portions of the roller shaft 259 protruding from both side walls 255 of the developing frame 251 of the developing cartridge 208 are guided inward in the width direction by the guide portions 283 of the swinging member 280 (see FIGS. 7A and 7B). The cartridge is introduced into the cartridge guide 237 from above. The developing cartridge 208 is moved downward while both end portions of the roller shaft 259 are guided by the cartridge guide portion 237. When the developing cartridge 208 is guided to the cartridge holding portion 238 (see FIG. 5) and the developing roller 207 contacts the photosensitive drum 205 as shown in FIG. 1, further pressing of the developing cartridge 208 is restricted, and the developing roller 207 is positioned with respect to the photosensitive drum 205. Thereafter, the developing cartridge 208 is slightly tilted forward. As a result, as shown in FIG. 5, the development pressing boss 260 of the developing cartridge 208 passes between the pressing cam 271 and the pressing portion 286 of the swinging member 280 and enters the lower side of the pressing cam 271. Is lifted from the lower side against the urging force of the pressing spring 272. As a result, the development pressing boss 260 is urged downward by the pressing cam 271 and the developing cartridge 208 is pressed downward. In this state, the pressing portion 286 of the swing member 280 is disposed at a position slightly spaced from the development pressing boss 260.
4). FIG. 9 is a side view of the linear cam. FIG. 10 is a main part perspective view showing a state in which all the developing cartridges are separated from the photosensitive drum.

As shown in FIG. 10, a pair of main body side plates 290 that are opposed to each other in the width direction are provided in the main body casing 202. In each figure after FIG. 10, only the right main body side plate 290 is shown.
A roller member 291 is provided at the front end of the main body side plate 290 so as to abut against the flange 233 of each second side plate 224 of the drum unit 204 from below and to guide the drum unit 204 slidably into the main body casing 202. It has been. The roller member 291 is rotatably supported by a roller shaft (not shown) that extends inward in the width direction from the main body side plate 290.

In addition, one main body reference shaft 292 is installed between the rear end portions of the left and right main body side plates 290.
When the drum unit 204 is mounted in the main casing 202, first, the front cover 203 (see FIG. 1) of the main casing 202 is opened. Then, the rear end edge of the flange 233 of the second side plate 224 of the drum unit 204 is brought into contact with the roller member 291 from above. Thereafter, when the drum unit 204 is moved rearward, the flange portion 233 of the second side plate 224 slides on the roller member 291, and the drum unit 204 is guided into the main body casing 202. After the roller unit 291 abuts on an inclined surface 234 (see FIGS. 2 and 3) provided on the front side of the flange 233, the drum unit 204 is moved downward as a whole, and then the cutout portion of the first side plate 223 is formed. When 231 comes into contact with the main body reference shaft 292 from above and from the front, further pressing of the drum unit 204 is restricted. Thereby, the mounting of the drum unit 204 in the main body casing 202 is completed.

The detachment of the drum unit 204 from the main body casing 202 is the reverse of the above.
5). Separation mechanism In the main body casing 202, a separation mechanism 301 for displacing each developing cartridge 208 to a first position where the developing cartridge 208 comes into contact with each photosensitive drum 205 and a second position where the developing cartridge 208 is separated from each photosensitive drum 205 is provided. Is provided.

The separation mechanism 301 synchronizes a linear motion cam 302 as an example of a pair of linear motion members, a rail 303 that holds each linear motion cam 302 so as to be linearly movable in the front-rear direction, and the pair of linear motion cams 302. And a synchronous movement mechanism 304 for linear movement.
(1) Linear motion cam The linear motion cam 302 is provided in a pair on both sides in the left-right direction in the main body casing 202. FIG. 10 shows only the right-hand linear cam 302. Since the left and right linear cams 302 have the same configuration, the right linear cam 302 will be described below.

As shown in FIG. 9, the linear motion cam 302 is integrally provided with a main body 305 and four cam portions 306 provided on the inner surface of the main body 305.
The main body 305 is formed in a substantially elongated rectangular shape in side view extending in the front-rear direction. A rear end portion of the main body portion 305 is cut out in a rectangular shape in a side view from the upper surface, and a rack gear 310 is formed at an upper end edge thereof. Moreover, the main-body part 305 is formed in cross-sectional substantially L shape, and the lower end edge is bent toward the width direction inner side.

The four cam portions 306 are provided corresponding to the developing cartridges 208 (see FIG. 3) for each color. The cam portion 306 protrudes inward in the width direction at intervals on the inner side surface of the main body portion 305, and is formed in a substantially rectangular shape in side view. The rear end portion of the cam portion 306 forms an inclined surface 307 that is inclined from the lower end edge toward the rear upper side.
Further, the rear three cam portions (three cam portions 306 other than the foremost cam portion 306) are formed so that the intervals between the adjacent cam portions 306 are equal. The rearmost cam portion 306 is formed such that the interval between the adjacent cam portions 306 is larger than the interval between the three rear cam portions 306.
(2) Rail A pair of rails 303 is provided on both sides in the left-right direction in the main body casing 202. Here, since the left and right rails 303 have the same configuration, the right rail 303 will be described below.

As shown in FIG. 10, the rail 303 extends in the front-rear direction and has a substantially U-shaped cross section, and each free end thereof is fixed to the main body side plate 290.
With the drum unit 204 mounted in the main body casing 202, the rail 303 is cut into a rectangular shape in a side view from the upper edge of the rail 303 at a position corresponding to each developing cartridge 208 (see FIGS. 2 and 3). Four cutout portions 308 are formed. Further, the rear end portion of the rail 303 is formed such that its lower surface extends rearward from the upper surface and the left surface.

On the inner side of the U-shaped portion of the rail 303, a linear cam 302 is arranged so that the cam portion 306 protrudes inward in the width direction. The linear cam 302 is slidably provided along the rail 303, and the rear end portion of the linear cam 302 is always exposed upward from the rear end portion of the rail 303 regardless of the position of the linear cam 302. is doing.
(3) Synchronous movement mechanism The synchronous movement mechanism 304, for example, generates a driving force for linear movement from the right-side linear cam 302 to the left-side linear cam 302 in accordance with the linear movement of the right-side linear cam 302. It is configured to communicate.

  That is, the synchronous movement mechanism 304 includes a right rack gear 310 formed on the upper surface of the rear end portion of the right linear cam 302, a right pinion gear 311 meshing with the right rack gear 310, and a rear end of the left linear cam 302. A left rack gear (not shown) formed on the upper surface of the section, a left pinion gear (not shown) meshing with the left rack gear, and a connecting shaft 312 on which the right pinion gear 311 and the left pinion gear are attached so as not to be relatively rotatable. I have.

Further, a driving force from a motor (not shown) is input to the left linear cam 302.
(4) Separation Pressing Operation FIG. 11 is a right side view when a part of the drum unit is cut, and shows a state where all the developing cartridges are in pressure contact with the photosensitive drum. FIG. 12 is a right side view when the drum unit is partially cut, and shows a state where only the black developing cartridge is in pressure contact with the photosensitive drum. FIG. 13 is a right side view when a part of the drum unit is cut, and shows a state where all the developing cartridges are separated from the photosensitive drum. FIG. 14 is a right side view when a part of the drum unit is cut, showing a state immediately before all the developing cartridges are in pressure contact with the photosensitive drum and the pressing portion of the swing member is separated from the developing cartridge.

The operation of the separation mechanism 301 will be described with reference mainly to FIGS.
As shown in FIG. 11, when the drum unit 204 is mounted in the main casing 202 (see FIG. 1) and the linear cam 302 is moved to the foremost position, the inclined surface 307 of each cam portion 306 (FIG. 9). And a contact portion 284 of the swinging member 280 disposed behind each of them is opposed to each other in a non-contact state with an interval in the front-rear direction. Between the inclined surface 307 of the foremost cam portion 306 and the abutting portion 284 of the swinging member 280 disposed behind it, the inclined surfaces 307 of the rear three cam portions 306 and the respective rear portions thereof are arranged. An interval larger than the interval between the swinging member 280 and the contact portion 284 is formed.

  In this state, each developing cartridge 208 is disposed at a contact position where the developing roller 207 and the photosensitive drum 205 are in contact with each other. Each pressing cam 271 is in contact with the developing pressing boss 260 of each developing cartridge 208 from above and presses each developing pressing boss 260 downward. Further, in this state, as shown in FIG. 7A, the protrusion 288 of the spring portion 287 of the swing member 280 is in contact with the lower end portion of the contact wall 289.

  From the state shown in FIG. 11, when a driving force of a motor (not shown) is input to an input rack gear (not shown) of the left linear cam 302 and the left linear cam 302 is moved rearward, As the linear cam 302 moves, the left pinion gear 311 rotates. The rotation of the left pinion gear 311 is transmitted to the right pinion gear 311 via the connecting shaft 312, and the right pinion gear 311 rotates in the same direction as the left pinion gear 311. As a result, the right-hand linear cam 302 moves rearward.

  As the linear movement cam 302 moves rearward, the inclined surfaces 307 of the three rear cam portions 306 come into contact with the contact portions 284 of the swinging member 280 disposed below each of the rear cam portions 306, and the rear The abutting portions 284 of the three swing members 280 on the side are pressed downward toward the rear side. By this pressing, each swinging member 280 rotates so that the pressing portion 286 is lifted upward with the first support shaft 239 inserted through the shaft hole 282 as a fulcrum. In the middle of the rotation of the swing member 280, the pressing portion 286 of each swing member 280 comes into contact with the developing press boss 260 positioned above the push member 260 from below to push up the developing press boss 260. As a result, the developing cartridge 208 corresponding to each color of yellow, magenta, and cyan is lifted upward against the pressing force applied from the pressing cam 271.

  Then, the movement of the linear cam 302 to the rear further proceeds, and as shown in FIG. 12, when the contact portion 284 of the swing member 280 contacts the lower surface of the three rear cam portions 306, yellow, magenta and The developing cartridge 208 corresponding to each color of cyan is disposed at the second position, and the developing roller 207 of each developing cartridge 208 is greatly separated from the photosensitive drum 205. At this time, the developing pressing boss 260 of the black developing cartridge 208 is pressed by the pressing cam 271. As a result, only the developing roller 207 of the black developing cartridge 208 is pressed against the photosensitive drum 205. At this time, as shown in FIG. 8, the protrusion 288 of the spring portion 287 of the swing member 280 is moved upward along the contact wall 289. Accordingly, the middle portion of the spring portion 287 is curved so as to bulge outward in the radial direction of the shaft hole 282, and a biasing force that biases the swinging member 280 in the clockwise direction in FIG. .

  Thereafter, when the linear movement cam 302 further moves backward from the state shown in FIG. 12, the inclined surface 307 of the foremost cam portion 306 is brought into contact with the abutting portion 284 of the swinging member 280 disposed behind the linear cam 302. It abuts and presses one end part of the foremost swing member 280 toward the lower rear side. By this pressing, the swinging member 280 rotates so that the pressing portion 286 is lifted upward with the first support shaft 239 as a fulcrum. During the rotation of the swinging member 280, the pressing portion 286 of the swinging member 280 comes into contact with the developing press boss 260 located above the pressing member 280 to push up the developing press boss 260. As a result, the black developing cartridge 27 is lifted upward against the pressing force applied from the pressing cam 271.

  Then, the backward movement of the linear cam 302 further proceeds, and as shown in FIG. 13, when the contact portion 284 of the swinging member 280 contacts the lower surface of the foremost cam portion 306, the black developing cartridge 208 is moved. Located at the second position, the developing roller 207 of the black developing cartridge 208 is largely separated from the photosensitive drum 205. As a result, the developing rollers 207 of all the developing cartridges 208 are separated from the photosensitive drum 205.

  13 can be returned to the states shown in FIGS. 11 and 12 by moving the linear cam 302 forward. At this time, when the inclined surface 307 of each cam portion 306 and the abutting portion 284 of the swinging member 280 located behind the cam portion 306 are separated from each other, the upward force applied from the swinging member 280 to the development pressing boss 260. Is released. Then, as shown in FIG. 14, the developing cartridge 208 is pressed downward by the pressing cam 271, and is placed at a contact position where the developing roller 207 and the photosensitive drum 205 come into contact with each other.

Each swing member 280 rotates in a direction in which the pressing portion 286 moves downward when the pressing portion 286 is pressed by the development pressing boss 260. After the development pressing boss 260 is returned to the position where the developing roller 207 and the photosensitive drum 205 are in contact with each other, the pressing force is applied by the urging force (the restoring force of the spring portion 287) of the spring portion 287 (see FIG. 7A). The part 286 further rotates in the direction of moving downward.
6). As described above, the drum unit 204 holds the four photosensitive drums 205 arranged in parallel. A developing cartridge 208 that holds the developing roller 207 is detachably mounted on the drum unit 204. The drum unit 204 is provided with a swing member 280 corresponding to each developing cartridge 208. Each swing member 280 is supported by a first support shaft 239 projecting from the drum unit 204 so as to be swingable. The drum unit 204 is attached to the inside of the main body casing 202 so as to be movable in the front-rear direction. A linear cam 302 is provided in the main body casing 202 so as to be linearly movable in the front-rear direction. A contact portion 284 is provided on one side of the swing member 280 with respect to the first support shaft 239. The linear motion cam 302 contacts the contact portion 284 during linear movement. A pressing portion 286 is provided on the other side of the swing member 280 with respect to the first support shaft 239. The pressing portion 286 faces the developing pressing boss 260 of the developing cartridge 208, and the developing roller 207 causes the photosensitive drum 205 to move the developing pressing boss 260 along with the linear movement after the linear cam 302 contacts the contacting portion 284. Press in the direction away from. Further, the swing member 280 includes a spring portion 287. The spring portion 287 has a biasing force in a direction to move the pressing portion 286 in a direction away from the developing pressing boss 260.

  In a state where each developing cartridge 208 is mounted on the drum unit 204, the pressing portion 286 of the swing member 280 faces the developing pressing boss 260 of each developing cartridge 208. By the linear movement of the linear cam 302, the abutting portion 284 of the swing member 280 is pressed against the linear cam 302, the pressing portion 286 of the swing member 280 is exposed to the development pressing boss 260 of the developing cartridge 208, and the developing roller 207 is photosensitive. Press in a direction away from the drum 205. Thereby, the developing roller 207 can be separated from the photosensitive drum 205. Further, when the linear motion cam 302 is linearly moved from this state, the pressing of the contact portion 284 of the swinging member 280 by the linear motion cam 302 is released, and the developing cartridge 208 of the developing cartridge 208 by the pressing portion 286 of the swinging member 280 is released. The pressing of the development pressing boss 260 is released.

  In this way, the swing member 280 is supported by the first support shaft 239 provided in the drum unit 204, and the swing member 280 swings about the first support shaft 239, so that the developing roller 207 is moved to the photosensitive drum 205. To and away from. Therefore, even if a pressing force is applied from the linear cam 302 to the swing member 280, the pressing force does not directly act on the drum unit 204. As a result, when the developing roller 207 is separated from the photosensitive drum 205, the position of the drum unit 204 with respect to the main body casing 202 can be prevented from shifting.

  Further, when the pressing of the developing pressing boss 260 of the developing cartridge 208 by the pressing portion 286 of the swinging member 280 is released, the pressing portion 286 moves away from the developing pressing boss 260 by the biasing force of the spring portion 287. To do. As a result, the posture of the swing member 280 can be stably maintained at a position where the pressing portion 286 of the swing member 280 does not press the development pressing boss 260 of the developing cartridge 208.

Further, the spring portion 287 comes into contact with the drum unit 204 (contact wall 289) and is elastically deformed. Thereby, the urging force of the spring portion 287 can be effectively applied to the swing member 280.
In addition, the swing member 280 includes a guide portion 283. The guide part 283 is inclined with respect to the width direction so that the inner side in the width direction is lower than the outer side in the width direction. Thus, when the developing cartridge 208 is mounted on the drum unit 204, the developing cartridge 208 is guided inward in the width direction by moving the developing pressing boss 260 of the developing cartridge 208 along the guide portion 283. . As a result, the developing cartridge 208 can be easily aligned in the width direction.

  The main body casing 202 has a main body reference shaft 292 extending in the axial direction of the photosensitive drum 205. The drum unit 204 is in contact with the main body reference shaft 292 in a state of being mounted in the main body casing 202. The drum unit 204 is positioned with respect to the main body casing 202 by this contact. The direction of the pressing force applied from the linear cam 302 to the contact portion 284 of each swinging member 280 is substantially the same as the direction in which the drum unit 204 contacts the main body reference shaft 292 (substantially front-rear direction). For this reason, even if a force acts on the drum unit 204 from the linear motion cam 302 via the swing member 280, the force is a force in substantially the same direction as the direction in which the drum unit 204 abuts against the main body reference shaft 292. . Therefore, when the developing roller 207 is separated from the photosensitive drum 205, the position of the drum unit 204 with respect to the main body casing 202 can be prevented from shifting.

  In addition, the linear cam 302 is provided with a cam portion 306 for pressing the contact portion 284 of the swing member 280 corresponding to the swing member 280. When the cam portion 306 comes into contact with the contact portion 284 of the swing member 280, the contact portion 284 of the swing member 280 is pressed by the cam portion 306. On the other hand, when the cam portion 306 is separated from the contact portion 284 of the swing member 280, the pressing of the contact portion 284 of the swing member 280 by the cam portion 306 is released. Therefore, the rocking member 280 can be rocked by a simple configuration in which the cam portion 306 is provided on the linear cam 302, and the developing roller 207 can be separated from the photosensitive drum 205.

  Further, the linear movement of the linear cam 302 causes the first state in which all the cam portions 306 are in contact with the contact portion 284 of the swing member 280, and the cam portion 306 corresponding to the black developing cartridge is in the swing member 280. The second state in which the other cam portions 306 are in contact with the contact portion 284 and the other cam portions 306 are separated from the contact portion 284 of the swing member 280, and the second state in which all the cam portions 306 are separated from the contact portion 284 of the swing member 280. It is possible to switch between three states.

  The developing cartridge 208 is provided corresponding to each color of black, yellow, magenta, and cyan. In the first state, the cam portion 306 comes into contact with the contact portion 284 of the all-color swing member 280, so that the development rollers 207 for all colors are separated from the photosensitive drum 205. In the second state, the cam portion 306 contacts the contact portion 284 of each swinging member 280 corresponding to yellow, magenta, and cyan, so that the yellow, magenta, and cyan developing rollers 207 are separated from the photosensitive drum 205, A black developing roller 207 contacts the photosensitive drum 205. In the third state, the developing roller 207 for all colors comes into contact with the photosensitive drum 205 by separating the cam portion 306 from the abutting portion 284 of the swing member 280 for all colors. For this reason, the yellow, magenta, and cyan developing rollers 207 can be prevented from being consumed by setting the second state when the monochrome image is formed.

  In addition, a contact surface of the swing member 280 with the contact portion 284 in the cam portion 306 is formed as an inclined surface 307 that is inclined with respect to the width direction. Therefore, the pressing force applied from the cam portion 306 to the contact portion 284 of the swing member 280 includes a force component in the width direction. As a result, since a force in the width direction acts on the drum unit 204, the drum unit 204 can be positioned in the width direction.

  Corresponding to each developing cartridge 208, a pressing mechanism 270 for pressing the developing cartridge 208 in the facing direction between the developing roller 207 and the photosensitive drum 205 is provided. By this pressing mechanism 270, the developing roller 207 can be pressed against the photosensitive drum 205. As a result, the toner can be satisfactorily supplied from the developing roller 207 to the photosensitive drum 205.

  The drum unit 204 is provided with a second support shaft 240. A pressing cam 271 is swingably supported on the second support shaft 240, and the pressing cam 271 is elastically pressed against the developing pressing boss 260 of the developing cartridge 208 by the pressing spring 272. By this pressing, the developing roller 207 can be pressed against the photosensitive drum 205.

FIG. 1 is a side sectional view showing an embodiment of a printer as an example of an image forming apparatus of the present invention. FIG. 2 is a perspective view of the drum unit as viewed from the upper left front side, showing a state where one developing cartridge is attached and the other developing cartridges are detached. FIG. 3 is a perspective view of the drum unit as viewed from the upper left front side, showing a state where one developing cartridge is being attached and detached and the other developing cartridges are detached. FIG. 4 is a front view of the drum unit. FIG. 5 is a left side view of the drum unit partially cut away. FIG. 6 is a left side view of the right second side plate. FIG. 7A is a side view of the swing member, and shows a part of the second side plate. FIG. 7B is a perspective view seen from the upper left rear side of the swing member. FIG. 7C is a perspective view of the swing member as viewed from the upper right rear side. FIG. 8 is a side view of the swing member, and shows a state where the swing member is swung in the direction in which the developing cartridge is moved from the first position to the second position. FIG. 9 is a side view of the linear cam. FIG. 10 is a main part perspective view showing a state in which all the developing cartridges are separated from the photosensitive drum. FIG. 11 is a right side view when a part of the drum unit is cut, and shows a state where all the developing cartridges are in pressure contact with the photosensitive drum. FIG. 12 is a right side view when the drum unit is partially cut, and shows a state where only the black developing cartridge is in pressure contact with the photosensitive drum. FIG. 13 is a right side view when a part of the drum unit is cut, and shows a state where all the developing cartridges are separated from the photosensitive drum. FIG. 14 is a right side view when a part of the drum unit is cut, showing a state immediately before all the developing cartridges are in pressure contact with the photosensitive drum and the pressing portion of the swing member is separated from the developing cartridge.

Explanation of symbols

201 Printer 202 Main Body Casing 204 Drum Unit 205 Photosensitive Drum 207 Development Roller 208 Development Cartridge 239 First Support Shaft 240 Second Support Shaft 260 Development Press Boss 270 Press Mechanism 271 Press Cam 272 Press Spring 280 Swing Member 283 Guide Portion 284 Contact Portion 286 Pressing portion 287 Spring portion 292 Main unit reference shaft 302 Direct acting cam 306 Cam portion 307 Inclined surface

Claims (10)

The device body;
A tandem type photosensitive unit that holds a plurality of photosensitive drums in a state of being arranged in parallel, and is mounted so as to be movable along the alignment direction of the photosensitive drums in the apparatus main body;
A developing cartridge provided corresponding to each photosensitive drum, holding a developing roller for supplying a developer to the corresponding photosensitive drum, and detachably mounted on the tandem photosensitive unit;
A linear motion member provided in the apparatus main body so as to be linearly movable in the alignment direction;
Corresponding to each of the developing cartridges, a first support shaft provided in the tandem type photoreceptor unit;
A swing member supported swingably on the first support shaft,
The swing member is
A contact portion provided on one side with respect to the first support shaft, wherein the linear motion member contacts during linear movement;
The predetermined portion is provided on the other side of the first support shaft, faces the predetermined portion of the developing cartridge, and moves the predetermined portion to the developing roller along with the linear movement after the linear movement member comes into contact with the contact portion. A pressing portion for pressing in a direction away from the photosensitive drum;
An image forming apparatus comprising: a spring portion having a biasing force in a direction to move the pressing portion in a direction away from the predetermined portion.   The image forming apparatus according to claim 1, wherein the spring portion abuts on the tandem photoconductor unit and elastically deforms.   The said rocking | fluctuation member is provided with the guide part which inclines with respect to the said axial direction so that the inner side of the said axial direction may become lower than the outer side of the axial direction of the said photosensitive drum. Image forming apparatus. The apparatus main body has a main body reference axis extending in the axial direction of the photosensitive drum,
The tandem photoconductor unit is in contact with the main body reference axis in a state of being mounted in the apparatus main body,
The direction in which the tandem photosensitive unit abuts against the main body reference axis is substantially the same as the direction of the pressing force applied from the linear motion member to the abutting portion of each swing member. The image forming apparatus according to claim 1, wherein the image forming apparatus is characterized.   The linear motion member is provided corresponding to each of the swinging members, and includes a cam portion that contacts the contact portion of the swinging member and presses the contact portion. The image forming apparatus according to any one of claims 1 to 4.   The cam portion includes a first state in which all the cam portions are in contact with the contact portion of the swing member by linear movement of the linear motion member, and at least one of the cam portions is the first member of the swing member. The arrangement is such that a second state where the cam portion is in contact with the contact portion and a third state where all the cam portions are separated from the contact portion of the swinging member can be taken. The image forming apparatus according to 5. The developing cartridge is provided corresponding to each color of black, yellow, magenta and cyan,
In the second state, the cam portion comes into contact with the contact portion of each swing member corresponding to yellow, magenta, and cyan, and the cam portion is moved from the contact portion of the swing member corresponding to black. The image forming apparatus according to claim 6, wherein the image forming apparatus is in a separated state.   The contact surface of the cam portion with the contact portion of the swing member is formed as an inclined surface inclined with respect to the axial direction of the photosensitive drum. The image forming apparatus according to claim 1.   Provided to correspond to each of the developing cartridges, and for pressing the developing cartridges in the opposing direction of the developing roller and the photosensitive drum in a state where each of the developing cartridges is mounted on the tandem type photoreceptor unit. The image forming apparatus according to claim 1, further comprising a pressing mechanism. A second support shaft provided in the tandem photoconductor unit;
The pressing mechanism includes a pressing member that is swingably supported by the second support shaft and abuts against the predetermined portion of the developing cartridge, and a spring that elastically presses the pressing member against the predetermined portion. The image forming apparatus according to claim 9, wherein the image forming apparatus is an image forming apparatus.

Images